The present invention relates generally to extrusion and in particular, to an extrusion die pre-heating device and method.
Extrusion involves the shaping of a work piece by forcing the work piece through an extrusion die using an extrusion press. During this process, the cross-sectional shape of the extruded work piece generally conforms to the shape of the extrusion die aperture. Metals and metal alloys can be extruded using either “hot extrusion” or “cold extrusion”, depending on the temperature at which the extrusion is carried out. During hot extrusion, the work piece and the extrusion die are both maintained at an elevated temperature. For example, aluminum and aluminum alloys are typically hot extruded at temperatures ranging from about 350 degrees Celsius (° C.) to about 500° C.
During the hot extrusion process, extrusion dies are typically pre-heated to the extrusion temperature in a separate oven prior to being installed in the extrusion press. This pre-heating reduces the time needed to bring the extrusion press to operating conditions, thereby increasing the throughput of the extrusion press.
Equipment for pre-heating extrusion dies has been previously considered. For example, U.S. Pat. No. 7,393,205 to Schwartz discloses a device for heating up extrusion dies prior to their installation in an extruder, whereby the extrusion dies are heated up to a prescribed temperature and kept at this temperature. The device comprises a gas-tight and thermally insulated oven housing that has at least one charging and discharging opening with an oven cover and, inside the oven housing, there is an impact nozzle field into which an extrusion die can be placed. The device is provided with a heating means that heats up a fluid that flows through the openings of the impact nozzle field.
U.S. Pat. No. 6,884,969 to Brach et al. discloses an infrared die oven having a die cradle for holding a die. A thermocouple is positioned within the die cradle to maintain it in direct contact with the die. A controller connected to the thermocouple continually reads the temperature of the die. When the die reaches a threshold temperature, the intensity of an infrared heating element in the oven is reduced. When the die reaches the desired temperature, the controller continuously adjusts the heater intensity to maintain the die at the desired temperature.
European Patent Application No. 0529198 to Perdersoli discloses a controlled-atmosphere furnace for preheating dies for extruding aluminum and alloys thereof. The furnace includes a supporting frame which delimits, at a portion of a side wall, at least one chamber which can be closed tight with respect to the outside environment, a chamber door which can be opened outward and has a supporting frame for a part to be preheated, and resistors for heating the chamber.
Although known devices and methods for extrusion die pre-heating may be adequate, improvements are generally desired. It is therefore an object at least to provide a novel extrusion die pre-heating device and method.